Method for folding an inflatable airbag for an airbag system

ABSTRACT

In a method for folding an airbag of an airbag system connected to a gas generator a tailored fabric consisting of two fabric layers defining the airbag volume is laid out flat and then engaged by a tool at the center of the length of the tailored fabric. At least a portion of the tailored fabric laid out flat is rolled in the direction toward the gas generator by rotating the tool so that the portion of the tailored fabric positioned at a side of the tool facing away from the gas generator is rolled into a double-layer roll. The tool is removed upon completion of the rolling process.

BACKGROUND OF THE INVENTION

The invention relates to a method for folding an airbag of an airbagsystem connected to a gas generator in which at least a part of thetailored, laid flat fabric consisting of two fabric layers defining theairbag volume is folded by rolling.

A method of the aforementioned kind is disclosed in U.S. Pat. No.5,492,367. The described airbag to be folded has a cylindrical gasgenerator inserted in its longitudinal direction between fabric layersof the tailored fabric such that the tailored fabric has a projectinglength on both sides of the gas generator which in the disclosed methodof folding is selected to be asymmetric. In a first folding step, theportions of the fabric laid out flat at the end faces of the gasgenerator are folded inwardly in the direction toward the gas generator.The thus formed partially folded tailored fabric is then partiallyfolded further by rolling whereby the portion having the greater lengthis rolled from the exterior in the direction toward the gas generatorand, subsequently, the roll formed on one side of the gas generator isthen covered by the fabric portion on the other side of the gasgenerator still laid out flat and then folded in a direction toward thegas generator.

This known folding method is relatively cumbersome due to the individualfolding steps. Also, due to the different degree of folding of thefabric portions on opposite sides of the gas generator, the inflation ofthe airbag is not sufficiently fast. It is therefore an object of theinvention to improve a folding method of the aforementioned kind suchthat the folding of the airbag is simplified to facilitate mounting andthat the unfolding time of the folded airbag becomes shorter.

SUMMARY OF THE INVENTION

The solution to this object results, including advantageous embodimentsand developments of the invention, from the contents of the claims whichare following this description.

The invention is in principle based on the idea that the tailored fabriclaid out flat is engaged at the center of its length by a tool and isrolled in a direction toward the gas generator so that the portion ofthe tailored fabric positioned at a side of the tool facing away fromthe gas generator, upon rotation of the tool in the direction toward thegas generator is pulled into the resulting roll such that a double layerroll of the folded airbag results and that at the end of the foldingprocess the tool can be moved out of the roll. The invention has theadvantage that due to the double layer rolled folding action performedby a tool mounting is simplified and is thus suitable for mechanizationby the use of the tool. Due to the double layer roll the unfolding timeof the folded airbag is shortened. With a suitable shape of the laidflat, tailored fabric, the invention in its simplest embodimentsuggests, especially for a tailored fabric connected only to one side ofthe gas generator, to perform folding by rolling in the direction towardthe gas generator without a previous partial folding step of portions ofthe tailored fabric.

According to one embodiment of the invention, it is suggested that thefolding process is performed by a two prong fork as a tool whereby oneof the prongs upon engaging the spread-out fabric is positioned aboveand the other prong is positioned below the fabric.

According to one embodiment of the invention, it is suggested that for atailored fabric that extends to both sides of the gas generator bothportions of the fabric adjacent to the gas generator are engaged by thetool and respectively transformed by rolling into the form of the doublelayer roll positioned on both sides of the gas generator.

According to one embodiment of the invention, the formation of a relieffold may be provided which is formed between the outer circumference ofthe gas generator and the outer circumference of the roll restingthereat, whereby, for example, the rolling process of the tailoredfabric is stopped at a spacing to the gas generator and the portion ofthe laid flat, tailored fabric between the gas generator and the roll isthen folded by being pushed together into the shape of a relief fold.

Inasmuch as the tailored fabric projects past the outer contour of thegas generator, according to one embodiment of the invention, it issuggested to fold the projecting portions of the tailored fabricinwardly or laterally and to further fold the partially folded tailoredfabric by rolling as is, in principle, known from the aforementionedU.S. Pat. No. 5,492,367.

Inasmuch as the fabric is connected to a cylindrical gas generator,according to one embodiment of the invention, it is suggested that for aone-sided connection of the tailored fabric to the gas generator theouter lateral portions projecting past the longitudinal extension of thecylindrical gas generator are folded inwardly toward one another andthat the multi-layer fabric package is then transformed into a doublelayer roll by a tool in the form of rolling tongs by rolling.

Instead of a simple folding over of a portion of the tailored fabricprojecting past the gas generator, according to one embodiment of theinvention, it may be provided that for a one-sided connection of thetailored fabric to the gas generator one of the portions projectinglaterally past the longitudinal extension of the cylindrical gasgenerator is transformed into a multi-layer folded package by foldingaids that engage parallel to the fabric layers and that the respectiveother projecting portion of the tailored fabric is then folded overinwardly, whereby afterwards the thus formed multi-layer fabric packageis then transformed by rolling with a tool in the form of rolling tongsinto the shape of the multi-layer roll.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawing one embodiment of the invention is represented which willbe explained in the following. It is shown in:

FIG. 1 A plan view of a gas generator with tailored airbag fabric laidflat during a first partial folding step;

FIG. 1a The object of FIG. 1 in section along line I--I of FIG. 1;

FIG. 2 The partially folded tailored airbag fabric according to FIG. 1in a plan view during a further folding step;

FIG. 2a The object of FIG. 2 in section along line II--II in FIG. 2;

FIG. 3 The partly folded tailored airbag fabric of FIG. 2 in plan viewat the start of the folding step by rolling;

FIG. 3a The object of FIG. 3 in section along line III--III of FIG. 3;

FIG. 4 The finished-folded airbag in a plan view;

FIG. 4a The object of FIG. 4 in a perspective view;

FIG. 5 The finish-folded airbag in another embodiment with relief foldin a representation according to FIG. 4a.

DESCRIPTION OF PREFERRED EMBODIMENTS

A tailored fabric 11 of an airbag is connected to one side of acylindrical gas generator 10 and is laid flat, as shown by the solidlines in FIG. 1. The fabric 11 is comprised, according to the sectionalview of FIG. 1a, of two fabric layers 12 that define the airbag volume.The fabric 11 extends with a first portion 13 and a second portion 14respectively past the longitudinal extension of the gas generator andthus projects from it.

In a first partial folding step the first projecting portion 13 of thetailored fabric 11 is folded by a non-represented folding aid in adirection so as to be parallel to the gas generator 10, whereby thefolding aid engages the fabric layers in parallel, by pushing parts ofthe fabric layers 12 into the tailored fabric 11 so that the firstprojecting portion 13 of the tailored fabric 11 is folded as shown inFIG. 1 in a dashed line.

As can be seen in FIG. 2, the other projecting portion 14 of the fabric11 is inwardly folded so that after completion of this partial foldingstep there are no portions of the tailored fabric 11 that project pastthe longitudinal extension of the gas generator 10.

The thus formed multi-layer fabric package formed from the tailoredfabric 11 is then further folded by rolling by engaging the center ofthe thus formed fabric package by tool 15 in the form of a two-prongfork whereby one prong is positioned above and the other prong ispositioned below the fabric package as can be seen especially in FIG.3a. By rotation of the tool 15 in the form of a fork in the direction ofthe gas generator 10 a double-layer roll 16 (FIG. 4a) is formed wherebythe portion of the fabric package positioned between the gas generator10 and the tool 15 forms the inner roll while the portion of the fabricpackage positioned at the side of the tool 15 facing away from the gasgenerator is pulled in by rolling and thus forms the outer portion ofthe double layer. Subsequent to the rolling action of the tool 15, thetool 15 is laterally removed from the formed roll 16 so that the shapeof the gas generator with attached folded-in airbag results, as shown inFIG. 4, respectively, 4a.

It is understood that according to the invention the partial foldingsteps carried out before rolling can be oriented and performed as afunction of the geometrical shape of the tailored fabric 11 forming theairbag as well as of the shape of the gas generator 10 in any othersuitable manner, whereby the thus prepared fabric package formed of thetailored fabric 11 is then finish-folded to a double-layer roll byrolling.

As can be seen in FIG. 5, it may be provided that between the roll 16and the outer circumference of the gas generator a relief fold isarranged which is produced, for example, by interrupting the rollingstep of the fabric 11 at a spacing to the gas generator 10 with aportion of flat fabric being positioned between the gas generator andthe roll 16 and by then pushing the roll 16 against the circumference ofthe gas generator 10 so that the relief fold 17 is produced by pushingthe tailored fabric section together.

The features of the object of these documents as disclosed in the abovedescription, the claims, the abstract, and the drawings may be importantindividually or in any suitable combination for realizing the inventionin its different embodiments.

The specification incorporates by reference the entire disclosure ofGerman priority document 197 19 524.5 of May 9, 1997, and ofInternational Application PCT/EP98/02664 of May 6,1998.

The present invention is, of course, in no way restricted to thespecific disclosure of the specification and drawings, but alsoencompasses any modifications within the scope of the appended claims.

What is claimed is:
 1. A method for folding an airbag of an airbagsystem connected to a gas generator, said method comprising the stepsof:a) laying out flat a tailored fabric (11) comprised of two fabriclayers (12) defining the airbag volume; b) engaging a center of the laidout flat tailored fabric (11) with a tool (15); c) rotating the tool(15) in a direction toward the gas generator (10) so that a portion ofthe tailored fabric (11) disposed between the gas generator and the toolis rolled in a direction toward the gas generator (10) so that a portionof the tailored fabric (11) positioned at a side of the tool (15) facingaway from the gas generator (10) is drawn into the resulting roll suchthat a double-layer roll (16) results; and d) removing the tool (15)from the roll (16).
 2. A method according to claim 1, wherein the tool(15) is a two-prong fork, wherein, in said step b), one of the prongs ispositioned above and the other prong is positioned below the tailoredfabric (11).
 3. A method according to claim 1, wherein the tailoredfabric (11) extends from opposite sides of the gas generator (10), suchthat two portions of the tailored fabric (11) are provided on oppositesides of the gas generator (10), wherein in said steps b) and c) eachone of said portions of the tailored fabric (11) is engaged by the tool(15) and rolled into a double-layer roll (16).
 4. A method according toclaim 1, further comprising the step of forming a relief fold (17)between the outer circumference of the gas generator (10) and the outercircumference of the roll (16) resting thereat.
 5. A method according toclaim 4, wherein, in said step c), rolling of the tailored fabric (11)is stopped at a spacing to the gas generator (10) and wherein in saidstep of forming a relief fold a portion of the tailored fabric (11)positioned between the gas generator (10) and the double-layer roll (16)is pushed together to form the relief fold (17).
 6. A method accordingto claim 1, further including, before said step b), the step of foldinginwardly at least a portion of the laid flat tailored fabric (11) byforming outer folding edges, wherein the tool (15) is in the form ofrolling tongs.
 7. A method according to claim 1, wherein the gasgenerator (10) is cylindrical and wherein the tailored fabric (11) isconnected to one side of the gas generator (10) such that outer fabricportions (13, 14) of the tailored fabric (11) project laterally past alongitudinal extension of the cylindrical gas generator (10), whereinthe method further includes, before said step b), the step of foldinginwardly the outer fabric portions (13, 14) to form a multi-layer fabricpackage, wherein the tool (15) is in the form of rolling tongs.
 8. Amethod according to claim 1, wherein the gas generator (10) iscylindrical and wherein the tailored fabric (11) is connected to oneside of the gas generator (10) such that portions (13, 14) of thetailored fabric (11) project laterally past a longitudinal extension ofthe cylindrical gas generator (10), wherein the method further includes,before said step b), the steps of transforming one of the portions (13)by a folding aid, engaging parallel to the fabric layers (12), into aninwardly folded multi-layer fold arrangement and folding inwardly theother portion (14) of the tailored fabric (11) to form a multi-layerfabric package, wherein the tool (15) is in the form of rolling tongs.